In November, Assembly members failed to agree on an Ulster Unionist motion to end double-jobbing by 2011.
BBC: Double payments to end for NI MPs who are MLAs
2.
He stepped down as part of Sinn Fein's commitment to end double-jobbing - where politicians hold more than one elected post.
BBC: Martin McGuinness
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And following the decision of Martin McGuinness to resign as an MP in order to avoid so-called "double-jobbing", by holding a seat in both the House of Commons and the Northern Ireland Assembly, a by-election is also expected in his Mid Ulster constituency.